Antarctic ozone hole getting smaller
The hole in the ozone layer over Antarctica is now 20% smaller than it was last year, according to leading scientists from New Zealand.Ozone measurements taken by the National Institute of Water and Atmospheric Research (NIWA) have shown that the hole peaked at around 24 million square kilometres this year, compared with 29 million square kilometres in 2003 (see related story).
"Measurements from the ground at Scott Base suggest that there is slightly more ozone this year that the average for recent years," NIWA atmospheric scientist Dr Stephen Wood stated. "But ozone levels are still lower than before the ozone hole started forming in the early 1980s."
A clear improvement in the state of the ozone layer has been seen by scientists since the Montreal Protocol was passed in 1989, reducing the quantity of man-made ozone depleting chemicals in the atmosphere (see related story).
However other factors, such as the Antarctic cold during the polar winter, which also contribute to ozone depletion are more difficult to control, according to Dr Wood, who cautioned against reading too much into the measurements just yet.
"We need to see smaller of less severe ozone holes over a number of years before we can say for certain that ozone is recovering," he warned.
The ozone-depleted air is currently well contained over Antarctica, Dr Wood said, with the only the extreme tip of South America at risk of being affected. But he also expressed concerns that New Zealand could be indirectly affected at the end of the year.
"When the ozone layer breaks up, ozone depleted air moves into surrounding areas. The later it breaks up, the higher the sun is in the sky over New Zealand and the larger the effect on UV levels," Dr Wood said. "If New Zealand experiences a combination of lower ozone with high sun and few clouds, skin-damaging UV levels can be extreme."
By Jane Kettle